Vibranium
Vibranium is an extremely rare material that is believed to have originated from another world and was transported to this planet through meteorites that struck it aeons ago. Due to its scarcity, it has only been found in small deposits, one of which was on a subterranean monster that attacked Sunagakure. This unique ore contains energy manipulating properties that allows an almost insurmountable durability. At the same time, it is completely nonreactive to chakra and natural energy, which severely limits its practicality in the ninja world. Vibranium works by absorbing the vibratory or kinetic energy that strikes it, while not being affected by it at all. This energy that is absorbs ends up being stored within the molecular bonds that make up the vibranium. Because of this, pure vibranium has an energy absorbing threshold depending on the quantity of vibranium. If this energy threshold is passed, the collective energy that was absorbed into that piece of vibranium all escapes at the same time in an explosion. Though, in order to reach that threshold an extremely large amount of energy would need to be absorbed and the exact extent of energy absorption has not been determined. Unfortunately, being completely non-reactive to chakra has its perks and downsides. A positive factor of this is that if any chakra-fueled attack was to strike a piece of vibranium then that attack would harmlessly strike and be dissipated by the material. A major downside is that chakra can not be channeled through materials made of vibranium, meaning that enhancing a tool made of the material would be impossible. Further examples are as follows. *If one were to make a full-body suit of vibranium, then they would not be able to absorb natural chakra as it would be blocked off by the layer of vibranium. Also, they would not be able to channel chakra to the outside world through any portion of their body that is covered in the material; this would make manipulation of the elements seen in almost all jutsu impossible. If one has a natural ability to manipulate the chakra within oneself in order to launch a jutsu, it would be unable to leave the suit and could potentially cause harm or death to the user. *If a weapon or tool is made out of vibranium: the user can not channel chakra through it to make it sharper, give it a longer range, manipulate its shape, or use it to absorb or reflect chakra. *If partial armor pieces are made, the blockage of natural chakra can be avoided but the rate at which it is absorbed would still be lessened by the parts covered in vibranium. This also means that if gloves or shoes are made out of the material, any jutsu that uses or is fired by that respective body part would end up being unable to leave. In the case of katon, this could be dangerous as it could result in self-immolation. Despite these negatives, the material still has many practical applications outside of combat and for those who do not intend to use it with chakra or any other kind of enhancing energy. Becquerel, who has collected a sizeable amount of the material, had managed to make an alloy that manages to no longer have an upper threshold of energy that can be absorbed. At the same time, the energy that is absorbed naturally and harmlessly dissipates over time. But, because it is still made partially of vibranium, it also shares the same traits in regards to chakra as its parent material. Any other alloys that happen to be made out of vibranium will also lack the ability to be enhanced further by any kind of chakra or natural energy because they are made out of the parent material.